Every day, large volumes of people travel by way of aircraft, making the airlines (the airport and/or aircrafts) attractive targets for terrorism, including aircraft hijacking and using hijacked aircraft as lethal weapons. Airport security provides a defense against such terrorism by attempting to stop would-be attackers from bringing weapons, explosive materials, and/or other potentially lethal contraband into the airport. Lines of defense have included Sky Marshals, metal detectors, luggage scanners, puffer machines (which can detect traces of compounds of interest), explosive detection machines (which detect volatile compounds given off from explosives using gas chromatography), and backscatter x-ray scanners that detect hidden weapons and explosives on passengers. Carry on luggage scanners have included x-ray based imaging systems which allow for “looking inside” luggage without opening the luggage. Computed tomography based scanners generate three dimensional 3D information indicative of the contents of the luggage. Unfortunately, such scanners tend to be expensive and have been primarily used to screen checked in luggage.
At security check points, x-ray line scanners typically are utilized to scan carry on luggage. FIG. 1 schematically illustrates an example line scanner 100, which includes a conveyor 102 that moves luggage 104 through a scanning region 106 located between an x-ray source 108 and a line of detectors 110 as the x-ray source 108 emits radiation 112 that traverses the scanning region 106 and illuminates the detectors 110. The line of detectors 110 generates signals indicative of the detected radiation, and the signals are processed to generate a single 2D projection image of the scanned region. However, 2D projection images do not provide volume information and, therefore, threats may be able to be hidden behind dense objects. Three dimensional (3D) data can be acquired using multiple detector line/x-ray source pairs located at different angles. Unfortunately, adding additional detector line/x-ray source pairs increases cost and consume additional space.
In view of at least the above, there is an unresolved need for other approaches for security scanners.